Prepare and evaluate a biodegradable contraceptive drug delivery system based on poly- -amino acid matrices. Specifically, the contractor shall: Synthesize polymers composed of poly- -amino acids; Characterize the synthesized polymers in terms of physical and processing characteristics; Evaluate the rate of polymer degradation both in vitro and in vivo; Ascertain the biocompatibility of selected polymers at the implant site (possible antigenicity of the polymers should be investigated); Prepare combinations of polymers with selected contraceptive drugs and ascertain the in vitro release of the drug and the in vivo release of the drug and its metabolism; and Select two or three of the most promising polymers for long term (three to six months) in vivo evaluation.